High volume fabrication of circuit boards, including memory modules, video/sound cards, and modem/fax cards requires rapid placement of numerous small electronic parts, such as chips, capacitors, resistors, and switches, onto circuit board substrates. Machines for circuit board manufacture generally include a means for feeding the appropriate parts to an arm. The arm lifts the individual parts and deposits them on the circuit board substrates, thus it may be known as a "pick-and-place" arm. Such machines also generally include a means for positioning the circuit board substrates beneath the arm so that the parts are correctly deposited, according to the necessary pattern of the particular circuit board. For example, see U.S. Pat. No. 5,153,983 to Oyama. A specific type of high speed pick-and-place machine that utilizes a rotating turret with a vacuum for uptake of parts and a forced air stream for their discharge is known as a "chip shooter," and is well adapted to mass production of circuit boards.
The usual method for feeding the parts to the arm is by using a tape reel. A tape, in this context, is a plastic or paper strip in which multiple cavities have been formed. The cavities are arranged in single file along the length of the strip, and an individual electronic part is placed in each cavity. The parts are then sealed with an adhesive tape covering that is affixed to the strip. The sealed tape is then wound into a large reel of parts. Parts are thus generally stored and supplied in this form, or they may need to be loaded into tape reels by the circuit board manufacturers at additional time and expense. In use, the tape reel must be repeatedly unwound and its covering peeled back to reveal the parts one by one for pick up by the arm. This means of feeding the parts is quite costly and time consuming as the tape materials are specialized and are used only once, the process of preparing the reels is very involved, requiring a special machine and a great amount of manpower, and the parts are usually loosely-placed in the cavities of the tape which necessitates correction of their orientations. Also, there is a significant time delay between presentation of one part to the arm for pick-up and the presentation of the next part. Thus, the parts are not quickly and efficiently picked up by the arm nor is their orientation assured.
Another method of feeding the parts is to use tube feeders. This entails plugging a plurality of tubes, each tube containing a row of a particular part, into the fabrication apparatus in a manner that allows a gravity or positive placement feed to place individual parts near the arm. When a tube is empty, it must be removed from the apparatus and replaced. This removal and replacement time causes an undesired delay in the manufacturing process. If the tubes have different quantities of parts, the apparatus needs to be stopped frequently for tube replacement. It is also difficult to see how many parts remain in the tube. In addition, the gravity feed of the tube feeders often results in a horizontal settlement time of the part before it may be picked up by the arm, which is short but significant for rapid, high volume manufacture. Simply put, tube feeders are not designed for mass production. U.S. Pat. No. 5,329,692 to Kashiwagi presents an electronic component mounting apparatus that utilizes both a tube feeder and a tape reel.
An object of the present invention is to provide a circuit board fabrication apparatus having a rapid, consistent, cost-effective, and reusable means of feeding parts in a correct orientation to an arm within the apparatus.
Another object is to provide an improved method for mass production of circuit boards, allowing longer running times of the circuit board fabrication apparatus.